interface List {
  readonly id: string,
  name: string,
  age?: number,
  [x: string]: any
}

interface Result {
  data: List[];
}

function render(result: Result) {
  result.data.forEach(item => {
    console.log(item.id, item.name);
    if (item.age) {
      console.log('find age: ', item.age);
    }
  });
}

let result: Result = {
  data: [
    {id: '1', name: 'ataola', age: 24},
    {id: '2', name: 'zjt', sex: 'male'}
  ]
};
render(result);
